INTRODUCTION: Sleep disturbances and impaired bed mobility are common in Parkinson's disease (PD). We examined whether objectively measured sleep efficiency is associated with axial motor impairment and explored its potential relationship with cognitive and mood profiles. METHODS: Twenty-eight patients with PD underwent single-night EEG-based sleep monitoring and assessment of nocturnal turning. Partial correlations between sleep metrics and scores on motor, cognitive and mood outcomes were analysed, controlling for age, sex and the MDS-UPDRS 3. Family-wise error (FWE) correction was applied within each sleep predictor. RESULTS: Poor sleep efficiency correlated with higher MDS-UPDRS axial subscore (rpartial = -.615) and this association survived stringent correction for multiple comparisons (FWE-p = .018). However, its associations with PIGD and clinically rated freezing of gait did not remain significant after the correction. Exploratory analyses showed the relationships of N1 percentage with mood disturbances and REM latency with self-reported freezing of gait, of which only the relationship of N1 percentage with depression score showed a trend towards significance after the correction (rpartial =.551, FWE-p = .074). CONCLUSION: Poor objective sleep quality was robustly associated with axial motor severity in PD, independent of overall motor burden. Sleep efficiency may represent a clinically accessible marker of shared brainstem-related pathology underlying axial dysfunction.